- The goal of this proposal is to establish methods for transdermal delivery of macromolecules, (e.g., peptides, proteins, and nucleic acids), with the potential for excellent control and low cost. The applicants will study enlarged transdermal aqueous pathways through the skin's stratum corneum (SC), that are created by secondary processes occurring after electrical creation of primary aqueous by "high- voltage" (HV) pulses (Uskin greater than or equal to 50V). Aims. Because of the many parameters involved, the aims are to study extensively and optimize pathway enlargement in vitro, followed by in vivo animal studies involving pathway creation, macromolecule transport, and initial evaluation of side effects. Significance. Successful pursuit of the Aims will establish a basis for transdermal drug delivery based on a compact, low-cost electrochemical technology. The envisioned technology will provide electronically controlled rapid delivery of water-soluble molecules ranging from conventional pharmaceuticals to macromolecules with short in vivo half lives. Thus, many of the uses of syringes could be replaced. Previous Work. Nonoptimized protocols show that (1) purely physical stimuli may create enlarged pathways, and (2) a nontoxic pathway-enlarging molecule created enlarged pathways which transported proteins at potentially therapeutic levels (100 micrograms per hour per centimeter squared). As required for future devices, transport appears to be concentrated at small skin sites (local transport regions; "LTRs") which occupy less than 10% of a 1 square centimeter area of skin. Prototype electrode/reservoir devices using microelectrodes and microholes provide painless pulsing in vivo. Both experiments (of the applicants and others) and theoretical modeling of localized electric fields show that side effects should be minimal. In one case, antibody molecules (IGG at 150,000 g per mole) were transported. Methods. The applicants will emphasize in vitro optimization of multiparametric enlarged pathway-creation protocols, using human, hairless rat, and pig skin, followed by in vivo assessment. They will use skin electrical resistance and fluorescent molecule flux measurements with image analysis to characterize the LTRs containing enlarged pathways. Theoretical analysis of localized fields, heating, pathway creation, and transport will be carried out, and is essential to optimizing enlarged pathways.